Engine

Abstract: The invention relates to an engine comprising a structural association of cylinders (24) in a cylinder block (20), a cylinder head (21), exhaust passages (47), intake passages (28), a crankshaft (9), injection nozzles (35), surge tanks (31), oil pump means (87), a power transmission belt (54) and/or other devices to arrange for a compact engine preferable to be used with an outboard motor.

Description: The present invention relates to an engine, especially the structural arrangement of the components thereof. The engine according to the present invention can be utilized not only as an engine for an outboard motor, but also as a general-purpose engine. In a common type of a prior art engine used in an outboard motor, the engine (a vertical engine) having a flywheel provided at an upper end of a vertically directed crankshaft protruding from an engine block is mounted in an outboard motor body case which is mounted to boat body through an antivibration mount. Such types of the outboard motors are disclosed, for example, in Japanese Patent Application Laid-open Nos.191610/87, 192917/88 and 192918/88. In these outboard motors, a ring gear is mounted around an outer periphery of the flywheel, and a starter motor is mounted above a side of the engine and meshed with the ring gear. A driving pulley of a valve-operating wrapping type transmission is provided at an end of the crankshaft adjacent and below the flywheel. In usual, an igniting power source coil and a charging power source coil are accommodated in the flywheel to constitute a dynamo and hence, the flywheel is of a downwardly-turned bowl-like shape. In such prior art outboard motor, the heavy flywheel having a large inertial moment, which largely influences the determination of the gravity center position of the engine, is farther spaced upwardly from the antivibration mount. And the crankshaft end opposite from the flywheel is coupled to a driving shaft for transmitting a driving force to a propeller. Therefore, factors of a torsional vibration are increased to exert not a little influence to the selection of the antivibration mount and hence, the selection of the antivibration mount must be taken into special consideration. In addition, not only the flywheel but also a starter must be mounted above the engine. Therefore, the gravity center position of the engine becomes high, which increases the moment required during tilting-up of the outboard motor, and also limits the freedom of the disposition of other auxiliaries, especially, the disposition of an electric equipment box for accommodating a CDI unit and a plurality of coils, other auxiliaries such as intake system auxiliaries or the like, in the case of a multi-cylinder (3 or more) engine. Further, in a 4-cycle engine used in the outboard motor, the driving pulley of the wrapping type transmission is provided as a valve operating device at the crankshaft end adjacent the flywheel. But the crankshaft end requires a large diameter for mounting the flywheel. Therefore, the diameter of the driving pulley must be increased and as a result, a driven pulley adjacent a cam shaft is also increased in size and has a shape occupying an area near an upper portion of a cylinder head, bringing about an increase in size of an upper portion of a rear end of an engine cover spaced from a tilting shaft. However, this portion of the engine cover is liable to interfere with a boat body structure, when the outboard motor is turned upwardly about the tilting shaft and hence, the unnecessary increase in size of this portion is undesirable and inconvenient even in respect of a moment required for the turning of the outboard motor. A lower portion of the outboard motor body case is formed narrow in order to reduce the underwater resistance of a submerged portion of the case to the utmost and to provide a reduction in weight. Therefore, an engine having a good mountability to such outboard motor body case is desired. In Japanese Utility Model Application Laid-open Nos.21509/91 and 23609/91, there has been proposed an engine in which a crankshaft is directed vertically and a flywheel is provided at a lower end of the crankshaft protruding from an engine block. Such an engine includes a transmission connected to that lower end of the crankshaft which is provided with the flywheel. Thus, this engine can not be applied directly as an engine for use in the outboard motor, and such prior arts do not suggest any means capable of solving problems inherent in the engine of the above-described type for use in the outboard motor. An outboard engine is disclosed, for example, in Japanese Patent Application Laid-open No. 267561/87. This engine includes a crankshaft disposed vertically, and two banks of cylinders disposed in an opposed V-shaped configuration. Each of the banks includes a cylinder block having three horizontal cylinders disposed in line along an axis of the crankshaft, and a cylinder head secured to an end face of the cylinder block in an axial direction of the cylinders. Intake ports are located on the inner sides of the V-shaped banks. Intake pipes connected to the intake ports extend in a direction away from the crankshaft at least partially along a center line of the angle of the V formed between the banks. A multi-barrel, single-chamber carburetor is provided for every pair of opposed cylinders. Exhaust ports are located on the outer sides of the banks. Exhaust passages connected to the exhaust ports, extend toward the crankshaft at least partially along the axes of the cylinders, and then extend to meet together in a single exhaust pipe. In such a prior art engine, an intake system including the intake pipes and carburetors, is disposed on the inner side of the V-shaped banks. Therefore, it is difficult to reduce the angle formed between the banks arranged in the V-shape for decreasing the width of the engine, to thereby reduce the size of the engine. Further, to reduce the angle of the V between the banks, the carburetor would have to protrude away from the crankshaft. This results in the problem that the length of the engine is increased, and the center of gravity of the engine itself is correspondingly displaced in a direction away from a crank chamber, which is not preferred depending upon conditions. There is another conventionally known multi-cylinder engine intake device. In such a device, the same number of intake pipes as that of cylinders extend from a surge tank having a predetermined capacity, and the intake pipes are connected to intake ports. A fuel injection device is disposed in each of the intake ports or in each of the intake pipes in the vicinity of the intake port, and a throttle valve is mounted on the surge tank for controlling the amount of air drawn into the tank. Such an intake device is disclosed, for example, in Japanese Patent Application Laid-open No. 60024/93. This intake device is applied to an in-line 4-cylinder engine for an outboard engine structure, and includes a surge tank disposed on one of the sides of the engine body at a location close to a crankcase. Four intake pipes (the same number as that of cylinders) extend from the surge tank and are connected to intake ports in a cylinder head, respectively. The upper three of the four intake pipes extend upwardly from the side of the surge tank and are then curved downwardly at their intermediate portions. The remaining lowermost intake pipe extends straight laterally and downwardly from a bottom of the surge tank. All of the intake pipes are disposed to extend along the side of the engine body. In such an engine, all the intake pipes extend from the single surge tank, and the total amount of air drawn must be provided by the single surge tank. Hence, the capacity of the surge tank is necessarily increased. As a result, if the capacity of the single surge tank is increased, it is difficult to accommodate the surge tank in an engine compartment in a compact manner. Therefore, there is almost no space for disposition of auxiliaries around the engine, resulting in a decreased degree of freedom for selection of positions for the disposition of the auxiliaries. Accordingly, it is an object of the present invention to provide a reduction in size of the engine and at the same time to improve the intake system and the engine fabrication and to improve further the mountability. This object is achieved with the features of claim 1. Due to above physical arrangement of flywheel, oil communication passage and exhaust passage it is possible to significantly reduce the necessary space without any structural effects on the intake system side and on the possibility of the engine fabrication. Furthermore mountability is enhanced. Further features are set force in the dependent claims. The above and other objects, features and advantages of the invention will become apparent from the following description of preferred embodiments taken in conjunction with the accompanying drawings. Figs.1 to 12 illustrate an embodiment of the present invention, wherein Fig.1 is a side view of the entire outboard motor; Fig.2 is a right side view of an engine; Fig.3 is a left side view of the engine; Fig.4 is a cross-sectional view of the engine; Fig.5 is a diagram illustrating a fuel supply system; Fig.6 is a view of an end of an engine block on the side of a cylinder head; Fig.7 is a vertical sectional view taken along various sections of the engine including an axis of a crankshaft; Fig.8 is an enlarged view of a portion shown in Fig.7; Fig.9 is a top view of an engine mount case; Fig.10 is a bottom view of the engine mount case; Fig.11 is a sectional view taken along a line 11-11 in Fig.7; and Fig.12 is a view of an end of the cylinder head on the side of a cylinder head cover. An embodiment of the present invention will be described with reference to Figs.1 to 12. Fig.1 is a side view of the entire outboard motor to which the present invention is applied. An outboard motor body 1 is mounted at a stern 3 through a mounting means 2. The outboard motor body 1 includes an outboard motor body casing 6 which comprises an engine mount case 4 and an extension case 5. An engine 7 is mounted on an upper portion of the outboard motor body casing 6 and covered at its upper portion with an engine cover 8. The open air is introduced into the cover 8 through an air intake port 8a. The engine 7 will be described hereinafter. A crankshaft 9 of the engine 7 is directed vertically, and a driving shaft 10 is connected to the crankshaft 9 and extends downwardly within the outboard motor body casing 6. The driving shaft 10 is connected at its lower end to a propeller shaft 12 through a forward and backward movement changing device 11. A propeller 13 is rotatively driven by an engine power transmitted thereto through the crankshaft 9, the driving shaft 10, the forward and backward movement changing device 11 and the propeller shaft 12. The mounting means 2 includes a bracket 15 fixed to the stern through bolts 14, and a swivel case 17 pivotally mounted on the bracket 15 for vertically swinging movement through a tilting shaft 16 provided at a front end of the bracket 15 to extend transversely. A swivel shaft 18 is rotatably carried in the swivel case 17 in a vertically directed manner. The outboard motor body casing 6 is connected to the swivel shaft 18 through upper and lower connecting members 19 and 19a. Thus, the outboard motor body casing 6, i.e., the outboard motor body 1 is vertically swingable about the tilting shaft 16 and turnable in counterclockwise and clockwise directions about an axis of the swivel shaft 18. Fig.2 is a right side view of the engine 7; Fig.3 is a left side view, and Fig.4 is a cross-sectional view. The terms "left" and "right" mean left and right when the outboard motor mounted at the stern 3 is viewed forwardly from rear (rightwardly from left in Fig.1). An engine body of the engine 7 includes an engine block 20, a cylinder head 21 and a cylinder head cover 22. The engine block 20 is constructed by integrally coupling a cylinder block portion 20a integrally provided with a skirt forming a half of a crankcase, with the remaining crankcase portion 20b by a bolt 23. Two sets of upper and lower pairs of cylinders 24, 24 arranged into a laterally V-shaped configuration are disposed within the engine block 20. More specifically, the engine 7 is a V-type 4-cycle engine with pistons 25 connected to the single crankshaft 9 directed vertically through connecting rods 26. Fig.6 is a side view of the engine block 20 on the side of the cylinder head 21. As can be seen from Fig.6, the cylinders 24 are four cylinders: a pair of cylinders 24a and 24b vertically arranged on the left side, and another pair of cylinders 24c and 24d vertically arranged on the right side. These cylinders are arranged in a zigzag manner such that the left cylinders 24a and 24b are higher in level than the right cylinders 24c and 24d. Such arrangement of the cylinders makes it possible to reduce the lateral width of the engine block, as compared with another V-type engine and to reduce the size of the engine 7. Intake passages 28 are provided in the cylinder head 21 in correspondence to the cylinders 24, as shown in Fig.4 with regard to the left (left in the outboard motor, i.e., lower as viewed in Fig.4) cylinder 24. The intake passages 28 are connected to the corresponding cylinders 24 through intake valves 29 and open into a side surface of the cylinder head 21. Intake pipes 30 are connected to such openings of the intake passages 28, respectively and extend along the side surface of the engine block 20 toward a crank chamber provided ahead. The intake pipes 30c and 30d shown in Fig.2 are those corresponding to the cylinders 24c and 24d shown in Fig.6, and the intake pipes 30a and 30b shown in Fig.3 are those corresponding to the cylinders 24a and 24b shown in Fig.6. Surge tanks 31L and 31R are provided on the laterally opposite sides of a front portion of the engine block 20, and the intake pipes 30a and 30b are in communication with the surge tank 31L, while the intake pipes 30c and 30d are in communication with the surge tank 31R. On the other hand, a throttle body 32 having a throttle valve therein is disposed on a front and central portion of the engine block 20, and is in communication with the surge tanks 31L and 31R through an air passage 33 which diverges laterally from the throttle body 32. Air is introduced from above into the throttle body 32 via an air introducing pipe 34. The air introduced from above via the air introducing pipe 34 is adjusted in flow rate within the throttle body 32 and then distributed into the left and right surge tanks 31. From the tanks 31, the air is supplied as combustion air through the intake pipes 30 into the corresponding cylinders 24, wherein fuel is injected from a fuel injection valve 35 and mixed with such air in the intake passages 28 (Fig.4). In Fig.2, reference character 32a is a throttle valve stem; reference character 32b is a link member; and reference character 32c is a fastener of a rubber or the like. In Fig.3, reference character 32d is a throttle valve opening degree sensor, and reference character 33b is an intake air temperature sensor. The surge tank 31 has a connection 33a to the air passage 33 on a side thereof, and has a capacity area extending vertically, i.e. upwardly and downwardly of the connection 33a. The volume of the capacity area is set as required, but a portion of the capacity area lying below the connection 33a is located out of a flow of air from the connection 33a to a connection with each intake pipe 30. Hence, should water enter an intake system, such portion also acts as a separating chamber. Reference character 93 is a drain bolt. Fig.5 is a diagram illustrating a fuel supply system. Reference character 37 is a fuel receiving pipe mounted in the outboard motor, and reference character 38 is a fuel delivering pipe mounted on a boat. By connecting these pipes 37 and 38, the fuel can be supplied from a fuel tank 39 mounted on the boat. Reference character 40 is a low-pressure filter, and reference character 41 is a low-pressure pump. The fuel pumped from the fuel tank 39 by the low-pressure pump 41 is once stored in a gas-liquid separator 42 and then supplied via a strainer 43, a high-pressure pump 44 and a high-pressure filter 45 to the fuel injection valve 35. These devices and pipes mounted on the outboard motor are disposed on the left side of the engine, as shown in Fig.3. The high-pressure pump 44 may be disposed within the gas-liquid separator 42. An exhaust valve 46 is mounted below the intake valve 29 in each of the cylinders 24 (see Fig.4), and an exhaust passage 47 is defined in the cylinder head 21 to lead to each of the exhaust valves 46. The exhaust passages 47 extend vertically through a widthwise central portion of the cylinder head 21, i.e., through an intermediate section between the array of the left cylinders 24a and 24b and the array of the right cylinders 24c and 24d to meet together at lower ends and open into the lower surface of the cylinder head 21 (see Figs.7 and 12). A valve operating mechanism comprising a cam 89a and a rocker arm 90a for the intake valves 29, and a cam 89b and a rocker arm 90b for the exhaust valves 46 is shown in Fig.12 only for the cylinders 24a and 24d, but of course, a similar valve operating mechanism is mounted for each of the other cylinders. As shown in Fig.2, a starter motor 48 is mounted on the right side of the engine block 20 with its output shaft 49 protruding downwardly. A driving gear 50 is mounted to the output shaft 49 and meshed with a ring gear which is integrally formed around an outer periphery of a flywheel 58 which will be described hereinafter. Fig.7 is a view of the engine 7 taken in various vertical sections including an axis of the crankshaft 9, with a section of the cylinder 24c and a portion of a section of the cylinder 24b being shown. The crankshaft 9 is directed vertically, as described above, and a cam shaft 51 is disposed in the cylinder head 21 in parallel to the crankshaft 9. Upper ends of the crankshaft 9 and the cam shaft 51 are passed through the engine block 20 and the cylinder head 21, respectively to project upwardly. Pulleys 52 and 53 are fixedly mounted at these upper ends. A belt 54 is wound around the pulleys 52 and 53. Thus, the cam shaft 51 is driven by the crankshaft 9 through the belt 54. Since the engine 7 is the 4-cycle engine, the diameter of the pulley 53 is twice the diameter of the pulley 52 in order to set the rotational ratio of the crankshaft 9 to the cam shaft 51 at 2 : 1. Reference characters 52a and 53a are controlling pick-up plates. A lower surface of the engine block is formed into an open portion 55, and a lower wall of the engine block 20 is formed by a closing plate 56 for sealingly closing the open portion 55. The closing plate 56 is detachably secured to the engine block 20 by bolts 57 (Figs.2 and 3). A lower end of the crankshaft 9 is rotatably passed through to project downwardly, and the flywheel 58 is secured to such lower end. Fig.8 is an enlarged view of a portion in the vicinity of the flywheel 58 shown in Fig.7. An axial bore 59 is provided in the lower end of the crankshaft 9, and a collar member 60 is fitted in the bore 59. A circumferentially projecting annular flange 60a is formed at a lower end of the collar member 60. The flywheel 58 is secured to the crankshaft 9 by fitting a circular bore centrally provided in a bottom plate portion 58a thereof over the collar member 60 and sandwiching their peripheral portions between a lower end face of the crankshaft 9 and the flange 60a to clamp them together by a bolt 61. The collar member 60 is also integrally fixedly secured to the crankshaft 9 bY the bolt 61. The flywheel 58 has a peripheral wall 58b projecting upwardly along an outer peripheral edge of the bottom plate portion 58a and is formed into a dish-like shape as a whole. A dynamo 64 is mounted within a space surrounded by the peripheral wall 58b and includes a rotor 62 fixed to the flywheel 58 and a starter 63 fixed to the closing plate 56. Further, a ring gear 65 is integrally formed around an outer periphery of the peripheral wall 58b of the flywheel 58 by shrink-fitting of a gear portion or by another means. The ring gear 65 is meshed with the driving gear 50 provided on the output shaft 49 of the starter motor 48 (Fig.2), and at the start of the engine, the crankshaft 9 is driven by the starter motor 48. The engine mount case 4 is coupled to the lower surface of the engine block 20 along with the closing plate 56 interposed therebetween by clamping thereof using the bolt 57. (In Fig.7, reference character 91 is a shift rod, and reference character 92 is a shift rod operating member connected to the shift rod 91 through a link system not shown, and Fig.8 is another sectional view of these portions and the bolt 57 is shown.) The engine mount case 4 extends further rearwardly up to the vicinity of the cylinder head, and is also connected to the lower surface of the cylinder head 21 into which the exhaust passage 47 opens. Fig.9 is a top view of the engine mount case 4, wherein reference characters 66a and 66b are packing surfaces extending along and abutting against the peripheral edge of the closing plate 56. A packing surface 67 is further provided to divide a space surrounded by the packing surfaces 66a and 66b into front and rear sections. The rear portion of the engine mount case 4 is in abutment against the lower surface of the cylinder head 21 through the packing surface 68 and is provided with an exhaust passage 69 communicating with the exhaust passage 47. The engine mount case 4 has peripheral walls 70a and 70b extending downwardly from the packing surfaces 66a and 66b, respectively, and an enclosure wall 71 extending downwardly from the packing surface 67 (Fig.7). All of the peripheral walls 70a and 70b and the enclosure wall 71 extend to positions lower than the flywheel 58. The periphery of the flywheel 58 is surrounded by the peripheral wall 70b and the enclosure wall 71. The lower end of the peripheral wall 70a is connected to a bottom plate 72a, and the lower end of the peripheral wall 70b is connected to a bottom plate 72b. These bottom plates 72a and 72b extend to positions below the central portion of the flywheel 58. However, the height (i.e., depth) of the peripheral wall 70b as measured from the packing surfaces 66a, 66b and 67 is lower than the height (i.e., depth) of the peripheral wall 70a and hence, the bottom plates 72b and 72a are superposed on each other in a vertically spaced apart relation below the central portion of the flywheel 58, and a mounting front opening 73 is defined therein to open forwardly. The driving shaft 10 for transmitting the rotation of the crankshaft 9 to the propeller 13 is carried in the bottom plates 72b and 72a to vertically extend through the opening 73. An upper end of the driving shaft 10 is inserted from below into an internal bore 60b (Fig.8) in the collar member 60 fitted to and spline-engaged with the crankshaft 9. The connecting member 19 for connecting the swivel shaft 18 and the engine mount case 4 to each other is also inserted from front into the opening 73. The connecting member 19 includes two left and right connecting rods 19a and 19b to extend longitudinally on opposite sides of the driving shaft 10. Tip ends of the connecting rods 19a and 19b are connected to the engine mount case 4 through a mount rubber 74. Fig.10 is a plan view of the engine mount case as viewed from below. A mounting surface 75 is formed into an annular shape on the lower surface of the engine mount case 4 (lower surface of the bottom plate 72a). Thus, the engine 7 is mounted on the extension case 5 through the engine mount case 4 by clamping the engine mount case 4 to the peripheral edge of the upper end of the extension case 5 with the mounting surface 75 interposed therebetween. An annular oil pan mounting surface 76 is also formed on the lower surface of the engine mount case 4 inside the mounting surface 75, and a peripheral edge of an upper end of an oil pan 77 is fastened to the oil pan mounting surface 76 by bolts 78, as shown in Fig.7. An opening 79 in an upper surface of the oil pan 77 communicates with the inside of the engine block 20 through an oil communication passage 80 defined in the engine mount case 4 and an opening 81 provided in the closing plate 56. And an oil returned from the crank chamber and accumulated on the closing plate 56 is passed through the opening 81 and the oil communication passage 80 and dropped from the opening 79 into the oil pan 77. However, the opening 81 is provided on the side opposite from the flywheel 58 with respect to the enclosure plate 71 of the closing plate 56. Therefore, the oil on the closing plate 56 cannot enter a portion of the flywheel 58 which is surrounded by the peripheral wall 70b and the enclosure wall 71. An exhaust pipe portion 77a is integrally formed at an upper portion of the oil pan 77 to protrude rearwardly, and an exhaust passage 82 is defined in the exhaust pipe portion 77a to communicate with the exhaust passage 69 in the engine mount case 4. The exhaust passage 82 communicates with a catalytic converter 83 juxtaposed outside the oil pan 77, and an exhaust gas purified in the catalytic converter 83 is passed through an exhaust pipe 84 and discharged from the lower portion of the extension case 5 into water. The oil stored in the oil pan 77 is drawn through a strainer 85 and an intake pipe 86 into an oil pump 87 and supplied from the oil pump 87 to various portions of the engine. The oil pump 87 is driven by the crank shaft 9 through a gear train 88 (see Fig.8). In general, the gravity center of the outboard motor body is offset toward the gravity center of the engine due to an influence of the heavy engine carried at the upper portion and is at a location higher than the tilting shaft. In the above-described embodiment, however, the flywheel 58 which was located at the uppermost portion of an engine in the prior art, is now provided at the lower end of the crankshaft 9, i.e., at the lower portion of the engine 7. Therefore, the gravity center of the engine 7 and thus the gravity center of the outboard motor body 1 is lowered to a position near the tilting shaft 16. Therefore, only a reduced moment is required to swing the outboard motor body 1 upwardly about the tilting shaft 16, thereby enabling an easy tilting-up or a prompt tilting-up. The flywheel 58 provided at the lower portion of the engine 7 is accommodated in a space between the engine block 20 and the connecting member 19. Therefore, the entire height of the outboard motor body 1 is relatively low. Further, the flywheel does not exist above the pulley 52 and hence, even if the pulley 52 is made sufficiently small in diameter, there is no problem in handling the pulley. Thus, the pulley 53 may be of a small diameter, leading to a reduction in size of the outboard motor body 1. Notwithstanding that the flywheel 58 protrudes downwardly, the engine 7 can be easily placed at a predetermined location through the engine mount case 4 having the peripheral wall 70 extending to a position below the flywheel 58 and particularly, can be easily and satisfactorily mounted on the outboard motor body 1. In addition, since the flywheel 58 has the upper and lower portions covered by the closing plate 56 and the bottom plate 72, and its periphery is covered by the peripheral wall 70b and the enclosure wall 71, water or the like is difficult to enter the area of the flywheel 58 from the outside and hence, the dynamo can be mounted without any influence exerted to positions around the dynamo 64. Further, the engine 7 in the present embodiment can also be utilized as a horizontal power source with the crank shaft 9 directed horizontally, by sealing the opening 81 in the closing plate 56, or by replacing the closing plate 56 itself and removing the oil pan 77. In the starter motor 48 of the engine 7, the output shaft 49 thereof protrudes downwardly from the motor body to engage, from above, the ring gear 65 formed on the flywheel 58 located below the starter motor 48 and hence, the need for water-proofness of such portion of the motor 48 can be avoided or reduced. In the engine 7, the power take-off driving shaft 10 and the flywheel 58 are mounted at the same end of the crankshaft 9 and therefore, the vibration of the engine due to the crankshaft 9 is reduced. It should be noted that some features of the present invention are of relevance for an engine, which may be used with an outboard motor, wherein a plurality of, for example four cylinders 24 are arranged in a row within the main block 20. Thus, the engine 7 is a serial 4-cylinder and 4-cycle engine, in which pistons 25 are connected to the vertically directed single crankshaft 9 through connecting rode 26. An oil pressurised by the oil pump 87 is fed to various bearing portions around the cam shaft 51 and via an oil passage (not shown) provided through the cylinder head 21, the cylinder block 20a and the crankcase 20b to an oil filter 99 mounted to the front surface of the crankcase 20b. The oil leaving the oil filter 68 flows into oil passages to reach main bearings of the crankshaft 9 to lubricate these bearings. Further, the oil flows through oil passages provided in the crankshaft 9 to reach a crank pin bearing and the inside of the cylinder 24 to lubricate the crank pin bearing and the inner surface of the cylinders. Cylinders 24 vertically arranged in a row or a single row are in communication with one another through oil bores so that the oil in each cylinder flows down and is discharged to a portion in the vicinity of the lower end of the crank shaft 9. However, this oil cannot flow into a chamber accommodating the flywheel 58 and is permitted to flow through oil passage 81 for returning of the oil around the outside of the flywheel 58 accommodating chamber to the oil pan communication portion of the mount case 4 and then returned into the oil pan 77. The oil which has lubricated the portion around the cam shaft 51 is passed through an oil passage 74 to an oil return bore and returned via oil return passages to the oil pan 77. The oil pan 77 depends from the mount case 4 into the extension case 5, thereby ensuring that the height of engine 7 mounted cannot be increased. The engine 7 is constructed such that the array of the cylinders 24a and 24b and the array of the cylinders 24c and 24d form a V-shape with each other and decrease the angle formed therebetween by defining the cylinders 24a to 24d within the single cylinder block 20. The exhaust passages 47 each have a simple shape and are centrally provided in the cylinder head 21. The intake passages 28 open into the opposite sides of the cylinder block 20 and are connected to the intake pipes 30a, 30b, 30c and 30d. Moreover, fuel is supplied into the intake passages 28 by the fuel injection nozzle 35. Therefore, the entire engine and particularly the structure around the cylinder block 20 and the cylinder head 21 is reduced in size and simplified. In addition, the intake passages 28 and the exhaust passages 47 are disposed in a substantially lateral, symmetric and balanced arrangement in the cylinder head 21, and the lengths of the passages for the left and right cylinder arrays are approximately equal to each other. Therefore, the flow of the intake and exhaust gases are equalised for each of cylinders 24a to 24d, leading to enhanced performance of the engine. As shown in Fig. 2, a starter motor 48 is mounted on a right area of the cylinder block 20 and an output shaft 49 of the motor 48 projects downwards. A driving gear 50 is mounted on the output shaft 49 and meshes with the ring gear 65. When the engine starts, the crankshaft 9 is driven by the starter motor 48. Since the surge tanks 31L and 31R are reduced in size and the intake pipes 30a to 30d are disposed in the upper area as described above, the starter motor 48 is disposed in a space formed on the lower right side below the engine body. The starter motor 48 is disposed at a location substantially above the flywheel 58 so that the output shaft 49 of the motor 48 extends downwards from the motor body into an engine mount case 4. The driving gear 50 mounted on the output shaft 49 meshes with the ring gear 65 provided around the outer periphery of the flywheel 58. In the engine 7, the intake pipes 30a to 30d corresponding to the cylinders 24a to 24d are located on laterally opposite sides of the engine body, i.e. the intake pipes 30a and 30b are located on one side and the intake pipes 30c and 30d are located on the other side. Therefore, it is easy to position the intake pipes 30a to 30d and to equalise the effective lengths thereof. The surge tanks 31L and 31R are also located laterally and are of a small size. Therefore, spaces for placement of the auxiliaries are available on the laterally opposite sides of the engine body. Further, the fuel supply system including the gas-liquid separator 42, and the oil filter 99 are placed in the space available on the left side, while the starter motor 48 is placed in the space available on the right side, thereby providing a good balance. Since the intake pipes 30a to 30d are disposed on the left and right sides of the engine body, and since the oil filter 99 is disposed in the space below the left side intake pipes 30a and 30b, it is possible to utilise the space at the side portion of the engine body to make the engine 7 compact. The location of the auxiliaries is not limited to the above-described locations, and the auxiliaries can be placed in any suitable location by utilising the spaces available on the opposite sides. Further, since air is supplied through the common throttle body 32 to the surge tanks 31L and 31R, it is not necessary to provide throttle valves in the surge tanks 31L and 31R respectively. Therefore, each of the surge tanks 31L and 31R is further reduced in size and simplified in structure, leading to a reduced cost. Moreover, since the throttle body 32 is mounted on the lateral center line of the engine, the intake devices are substantially laterally symmetric. Further, the auxiliaries are also substantially laterally symmetric with good balance. Therefore, the engine according to the present invention has a good, balanced configuration with good weight distribution as a whole. The engine is especially suitable to be in a localised place such as the engine compartment in the upper area in the outboard engine structure. The engine mount case 4 is coupled to the lower surfaces of the cylinder block 20a and the crankcase 20b by fastening it to the closing plate 56 using bolts 57 (Figs. 2 and 3). The engine 7 is mounted on the motor case 5 through the engine mount case 4. The engine mount case 4 further extends rearwardly and is also coupled to the lower surface of the cylinder head 21 into which the exhaust passages 47 open. Inside the motor case 5, the oil pan 77 is fastened at its upper end peripheral edge to the lower surface of the engine mount case 4. The oil pan 77 has opening 79 in its upper surface. The opening 79 is in communication with the interior of the cylinder block 20a and the crankcase 20b through oil communication passage 80 defined in the engine mount case 4 and opening 81 provided in the closing plate 56. Oil accumulated on the closing plate 56 passes through the opening 81 and the oil communication passage 80 and drops from the opening 79 into the oil pan 77. The exhaust passage 82 is defined in a partitioned manner in the oil pan 77 to communicate with a catalytic converter 83 juxtaposed outside the oil pan 77. The exhaust passage 82 is also in communication with the exhaust passages 47 in the cylinder head 21 through an exhaust passage 69 defined in the engine mount case 4. The oil stored in the oil pan 77 is drawn through strainer 85 and intake pipe 86 into oil pump 87 and supplied from the oil pump 87 to various portions of the engine. As can be seen from Figs. 8 and 7, the oil pump 87 is mounted in the cylinder block 13 at a lower and left location close to a longitudinal center line. This location corresponds to a position below the cylinder 24b. More specifically, as shown in Fig. 6, the left cylinders 24a and 24b are disposed at a level higher than the right cylinders 24c and 24d. Therefore, a space is created below the cylinder 24b and hence, the oil pump 87 is disposed in this space. The oil pump 87 has a rotor shaft which rotatably projects downwardly through a pump casing. A driven gear is fixedly mounted at a lower end of the rotor shaft. This driven gear meshes with an intermediate gear which meshes with a driving gear fixedly mounted on the crankshaft 9. Thus, the oil pump 87 is driven by the crankshaft 9 through the train 88 of the gears. The oil discharged from the oil pump 87 passes to the oil filter 99. The oil filter 99 is positioned to project from the left side of the cylinder block 20 at a location to the rear of the gas-liquid separator 42. In the present embodiment, one array of cylinders 24a and 24b is positioned in a higher level than the other array of the cylinders 24c and 24d to reduce the size of the engine body, and the oil pump 87 is located in the space created below the cylinder 24b which is disposed at the higher level. Therefore, the entire engine is small in size and compact. The present invention may be embodied in other specific forms without departing from the spirit and essential characteristics thereof. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, rather than the foregoing description.

Claims: An outboard motor comprising a V-type engine (7) and an engine mount case (4) for mounting of said engine, the engine having a plurality of cylinders (24) arranged in a V configuration, a crankshaft (9) directed in a vertical direction, wherein a flywheel (58) is provided at a lower end of said crankshaft (9) and a closing plate (56) on the lower side of the engine (7), and wherein an oil communication passage (80) is defined in said engine mount case (4) at a location rearwardly of said flywheel (58) and an opening (81) is provided in said closing plate (56), an opening (79) in an upper surface of an oil pan (77) communicating with said oil communicating passage (80) and said opening (81), said opening (81) being provided on the side opposite from the fly wheel (58) with respect to an enclosure wall (71), and wherein an exhaust passage (69) for passage of the exhaust from said engine (7) is defined in said engine mount case (4) at a location rearwardly of said oil communication passage (80), wherein an exhaust pipe portion (77a) being integrally formed at an upper portion of the oil pan (77) to protrude rearwardly. The outboard motor according to claim 1, wherein said engine mount case (4) has a peripheral wall which extends below the fly wheel (58) to surround at least a portion of the periphery of said flywheel (58). The outboard motor according to claim 2, wherein said engine mount case (4) comprises a bottom plate portion (70b) mounted at the lower part thereof and covering a lower portion of said flywheel (58) and comprising enclosure wall portions (70a, 70b, 71) for selectively surrounding the entire periphery of said flywheel (58) in cooperation with an peripheral wall of said engine mount case (4), said oil communication passage (80) and said exhaust passage (69), respectively. The outboard motor according to anyone of claims 1 to 3, wherein the oil communication passage and/or the exhaust passage are formed within the engine mount case (4) as passages therein.

Inventors: KOISHIKAWA KOUJI, KUWABARA SHIGEAKI, SUZUKI HITOSHI, TSUNODA MASAKI, WATANABE YOSHIMI, KOISHIKAWA, KOUJI, KUWABARA, SHIGEAKI, SUZUKI, HITOSHI, TSUNODA, MASAKI, WATANABE, YOSHIMI, Koishikawa, Kouji, K.K. Honda Gijutsu Kenkyusho, Kuwabara, Shigeaki, K.K. Honda Gijutsu Kenkyusho, Suzuki, Hitoshi, K.K. Honda Gijutsu Kenkyusho, Tsunoda, Masaki, K.K. Honda Gijutsu Kenkyusho, Watanabe, Yoshimi, K.K. Honda Gijutsu Kenkyusho
Applicants: HONDA MOTOR CO LTD, HONDA GIKEN KOGYO KABUSHIKI KAISHA
Application year: 1994
Main classification: F02B61
IPC codes: F02B75, F02F1, F02B61, F01M11